The invention relates to a packing assembly for sealing the annulus between the inside wall of a hollow cylindrical member and the outside wall of a second cylindrical member disposed therein and more particularly, it relates to a packing assembly for sealing the annulus between the inside wall of a wellhead and the outside wall of a casing or tubing hanger which is supported therein.
Heretofore, a great variety of packing assemblies have been used for sealing in wellheads and these generally employ elastomeric materials in the sealing elements. Such packing assemblies are susceptible to destruction by fire and at elevated temperatures short of fire conditions tend to deteriorate to such degree that their sealing capabilities are seriously impaired. Metal packing rings, on the other hand, have the advantage of holding up well under high pressure and temperatures but do not seal effectively where the coacting sealing surface has been galled or otherwise damaged.
Accordingly, it is a general object of the invention to provide an improved packing assembly for sealing an annulus as in a wellhead assembly, which is effective for sealing under high pressure and high temperature conditions and wherein the packing assembly can be mechanically activated.
Another object is to provide a packing assembly for sealing an annulus which includes the combination of metal-to-metal seals and lubricating packing seals and which can be reinforced in emergency conditions by the injection of a sealing plastic or fluid.
A further object is to provide a packing assembly which provides the combination of metal-to-metal seals and lubricating packing seals and which can be mechanically activated by the application of a carefully controlled axial compression force.
A still further object is to provide a packing assembly with both metal seal rings and lubricating packing rings which can be mechanically activated by the application of an axial compressive force to achieve a controlled radial expansion of the metal and lubricating packing seal rings.